Paul Johnson, 49, of Stafford Township, New Jersey, was snatched on Saturday by a group calling itself "Al-Qaida in the Arabian Peninsula". The organisation is believed to be headed by al-Qaida's chief in the kingdom, Abd Allah Aziz al-Muqrin.
A hooded man read a statement on the tape which was released on Tuesday. As he was reading, a subtitle on the screen identified him as al-Muqrin.
His statement was similar to a printed message on the website that carried the name of al-Qaida in the Arabian Peninsula. It said the group gave Saudi authorities 72 hours to release "mujahidin" fighters or it would kill the hostage.
The tape, which was first aired by CNN, showed Johnson sitting in a chair with his profile to the camera, a large tattoo on his left arm.
It displayed his Lockheed Martin identification card. Johnson was employed by the American military giant and worked on Apache helicopters.
Adil al-Jubair, foreign-affairs adviser to the Saudi government, said shortly after the video appeared that the kingdom would consult with the US administration about how to proceed, but Riyadh like Washington has a strict no-negotiation policy.
"We don't negotiate with terrorists. We don't negotiate with hostage-takers," al-Jubair said in an interview on CNN.
The Saudis ruled out negotiations
with Paul Johnson's captors
Al-Jubair denounced Johnson's captors, but said it was premature to be able to verify any of the information on the video, saying, "We can't simply go with what appears on web sites."
"It shows the cruel and inhuman face of the enemy we're dealing with," al-Jubair said.
The statement on the website says the holy warriors of the Arabian Peninsula's Falluja Brigade has "hit" the engineering team that "oversees the development of the American Apache helicopter that attacks Muslims in Palestine and Afghanistan".
It says: "The Falluja Brigade has killed the director of this team and kidnapped one of its engineers, Paul Johnson, and if the tyrannical Saudi government wants their American master to be released, then they have to release our holy warriors that are held in Hair, Ruweis and Alisha prisons within 72 hours of this statement's date."
"We can't simply
go with what appears
Foreign Affairs adviser to the Saudi government
The day Johnson was seized, armed dissidents shot dead another American, Kenneth Scroggs from Laconia, New Hampshire, in his garage.
Scroggs was the third Westerner killed in a week. An Irish cameraman for the BBC was shot dead on 6 June and another American was killed in his garage on 8 June.
Saudi security forces arrested an armed dissident north of Riyadh on Tuesday as they stepped up their presence in and around the city in a hunt for Johnson's captors.